• 한국콘텐츠학회:학술대회논문집
• /
• 한국콘텐츠학회 2003년도 춘계종합학술대회논문집
• /
• pp.466-469
• /
• 2003

본 논문은 TDM 방식을 적용한 WDM/TDM 네트워크에서 광경로를 설정하기 위한 분산제어 방식을 제안하였다. 제안된 분산 제어 방식에서는 블록킹 확률을 줄일 수 있도록 후방 예약 방식을 사용하였다 예 약 실패를 최소화하기 위해 여러 채널을 예약하는 진취 적 예 약 방법과 단지 하나의 채널을 예 약하는 보수적 예약 방법을 적용하여 두 개의 방법을 시뮬레 이 션을 통해 비교하였다.

• Journal of Communications and Networks
• /
• 제6권3호
• /
• pp.245-257
• /
• 2004

Driven by the growing number of the mobile subscribers, efficient channel resource management plays a key role for provisioning multimedia service in the next generation personal communication systems. To reuse limited channel resources, diminishing the coverage areas of cells seems to be the ultimate solution. Thus, however, causes more handover events. To provide seamless connection environment for mobile terminals and applications, this article presents a novel handover scheme called the intelligent channel reservation (ICR) scheme, which exploits the location prediction technologies to accurately reserve channel resources for handover connections. Considering the fact that each mobile terminal has its individual mobility characteristic, the ICR scheme utilizes a channel reserving notification procedure (CRNP) to collect adequate parameters for predicting the future location of individual mobile terminals. These parameters will be utilized by the handover prediction function to estimate the expected handover blocking rate and the expected number of idle channels. Based on the handover prediction estimations, a cost function for calculating the damages from blocking the handover connections and idling channel resources, and a corresponding algorithm for minimizing the cost function are proposed. In addition, a guard channel decision maker (GCDM) determines the appropriate number of guard channels. The experimental results show that the ICR scheme does reduce the handover-blocking rate while keeping the number of idle channels small.

• International Journal of Internet, Broadcasting and Communication
• /
• 제8권4호
• /
• pp.1-10
• /
• 2016

This paper considers WiMedia UWB network based wireless ship area network (WSAN) so as to support high-quality multimedia video data services and important shipboard control data. In this paper, prioritized contention access (PCA) and distributed reservation protocol (DRP) based on WiMedia UWB (ECMA-368) MAC protocols are combined and proposed to support mixed high-quality video traffic and shipboard control data traffic applying varying DRP and PCA data periods according to channel condition and link parameter ptimization. It is shown that the proposed dynmaic channel allocation of WiMedia UWB MAC protocol can provide reliable mixed video and shipboard control data traffic as well.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권3호
• /
• pp.1152-1167
• /
• 2018

In this paper, I propose an application layer cooperative congestion control scheme for safety message broadcast in vehicular networks, called CMS, that adaptively controls a vehicle's safety message rate and transmit timing based on the channel congestion state. Motivated by the fact that all vehicles should transmit and receive an application layer safety message in a periodic manner, I directly exploit the message itself as a means of estimating the channel congestion state. In particular, vehicles can determine wider network conditions by appending their local channel estimation result onto safety message transmissions and sharing them with each other. In result CMS realizes cooperative congestion control without any modification of the existing MAC protocol. I present extensive NS-3 simulation results which show that CMS outperforms conventional congestion control schemes in terms of the packet collision rate and throughput, especially in a high-density traffic environment.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2011년도 춘계학술대회
• /
• pp.336-339
• /
• 2011

실시간 위치 인식 및 추적 시스템에서 다수의 이동노드가 존재하는 경우 매우 복잡한 데이터 흐름이 발생한다. 단일 게이트웨이가 존재하는 네트워크에서 센서 노드가 수집한 각 종 데이터는 시간이 경과함에 따라 일정한 경로를 따라 전송된다. 멀티게이트웨이가 존재하는 네트워크 구성에서는 수집된 데이터가 단순한 경로가 아닌 다양한 경로를 따라 전송된다. 이러한 데이터는 많은 노드에서 혼잡을 발생시켜 네트워크 성능을 크게 저하 시킨다. 본 논문에서는 기존의 연구와 달리 멀티 게이트웨이를 갖는 수중센서 네트워크 환경에서 효율적인 통신을 위하여 각 노드들 간의 데이터 충돌을 최소화하고 QoS(Quality of Service)를 보장할 수 있는 MAC(Media Access Control) 프로토콜을 제안한다. 제안된 프로토콜에서 데이터 전송을 원하는 소스 노드는 하나의 RTS 패킷을 이용하여 다수의 목적 노드와 한번에 채널 예약을 한다. 소스 노드는 이웃 노드와의 측정된 전파지연 정보를 이용하여 CTS 응답 시간을 스케쥴링(Scheduling) 함으로써 충돌 없이 채널을 예약한다. 예약이 완료된 후 소스 노드는 여러 목적 노드에서 순차적으로 DATA 패킷을 충돌 없이 전송한다. 제안된 프로토콜은 시뮬레이션을 통해 기존 연구에서 제안된 방법과 성능을 비교하고 결과를 분석 및 평가한다. 성능 비교 분석결과, 제안된 방법이 더 좋은 효율과 지여 등의 성능을 가짐을 확인하였다.

• 대한임베디드공학회논문지
• /
• 제2권1호
• /
• pp.53-59
• /
• 2007

Wimedia UWB(Ultra-Wideband) platform provides data rates up to 480Mbps in WPAN (Wireless Personal Area Network). Wimedia conformant devices access to the channels through superframe concept for communications. As the channel resource is limited, the optimal channel time required for each device needs to be estimated to share the resource efficiently among the devices. In this paper, we propose a scheme to estimate the required channel time in a super frame to satisfy the QoS of the application on a device. The channel time is estimated from the service rate which is computed from the TSPEC of the application. In the process of the estimation, we take the frame overhead for data transmission as well as the overhead due to the acknowledgement scheme, preamble, and MDSU size into consideration. We also analyze and compare the throughputs for different acknowledgement scheme, preamble, and MDSU size situations. The estimated channel time required for a given service rate is allocated in the unit of MAS(Medium Access Slot).

• 한국정보기술응용학회:학술대회논문집
• /
• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
• /
• pp.199-201
• /
• 2005

USB has arguably become the most successful PC peripheral interconnect ever defined. As appearing UWB, wireless USB (WUSB) emerges very popular technology. However, the distributed Medium Access Control (MAC) does not harmonize with the topology of WUSB. In this paper, we address a novel MAC protocol for conformity with WUSB. The protocol is to handle negotiation on Distributed Reservation Protocol (DRP) including the channel time slot of WUSB.

• 전자공학회논문지S
• /
• 제36S권3호
• /
• pp.1-7
• /
• 1999

일대다 형상을 갖는 통신시스템에서 많이 고려되는 예약 알로하 방식 매체접속제어 프로토콜의 성능은 예약 채널과 데이터 채널의 분배 양식에 의해 달라진다. 본 논문에서는 이 프로토콜을 직렬 2단 대기열 모델로 근사화하고, 데이터의 지연을 성능 척도로 하여 이를 줄이는 세가지 채널 할당 방식을 제시하였다. 그리고 이들에 대한 모의실험을 통해 그 동작 특성을 규명하고 성능을 평가하였다. 그 결과 이들의 성능은 트래픽의 특성, 특히 데이터 길이의 분산에 크게 의존하며, 일반적으로는 데이터에 우선권을 주는 방식이 우수하나, 데이터 길이의 분산이 큰 경우에는 비례배분 할당 방식이 우수한 것으로 평가되었다.

• 대한전자공학회논문지
• /
• 제26권10호
• /
• pp.1462-1470
• /
• 1989

This paper aims at investigating the Demand Assigned Multiple Access(DAMA) system for the packet-switched Satellite Communication. An onboard processor of the multisport beam satellite incorporates the ground controller to macimize the packet transmissions for each slot. 'Request Following' trnasmission mode is introduced as a transmission strategy of ground station under the control of its zone controller. The combined scheme of reservation channel access and contention channel access was proposed by Lee & Mark[3] for improving the Delay-Throughput performance. Our scheme provides less communication delay of approximately max. 200msec for achieving the corresponding throughput than the Lee & Mark's work does. Delay versus Throughput curves as well as Delay versus Traffic parameter curves are obtained. Numerical results obtained through the analysis and by the computer simulation show that the proposed scheme provides the low average packer delay even under the condition that the number of transponders (M)is below the half of the number of zones(N).

• 산업기술연구
• /
• 제22권B호
• /
• pp.175-184
• /
• 2002

In this paper, we proposed separate queue scheme in each hierarchical cell for effective use of wireless channel. This method reduces the blocking rata of high speed mobile station's handoff in hierarchical cellular systems. Basically for the high speed mobile stations channels are allocated in macrocell and for the low speed mobile stations channels are allocated in microcell. In order to reduce the rate of forced handoff termination, some reservation channels are employed for the fast handoff calls in the macrocells. And the queue is located in each cell to be able to store handoff requests and takeback requests. The overflowed mobile station are able to perform takeback as soon as a corresponding channel is available.